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Biomedical subjects

M Akashi

Publications and source records attributed to M Akashi.

At least 73 records · Page 4Linked to original sources

In vivo induction of cytotoxic T lymphocytes specific for a single epitope introduced into an unrelated molecule.

Cytotoxic T lymphocytes (CTLs) recognise antigenic peptides in the context of major histocompatibility complex (MHC) class I molecules on virus-infected cells. The formation and transportation of antigenic peptides to class I MHC in the cells are multi-step reactions known as antigen processing. In order to design a good DNA vaccine, it is important to dissect the specificity of antigen processing. Here we describe the construction of an epitope-based plasmid vector as a device to investigate antigen processing in transfected cells. The epitope-based plasmid vector was constructed by insertion of an epitope-encoding minigene into the lacZ gene. We used a CTL epitope on influenza A virus nucleoprotein (NP366-374 epitope) as a model. Upon transfection, the epitope-based plasmid vector induced the expression of NP epitope antigenically as well as immunogenically. Immunization of mice with plasmid-transfected cells was able to induce NP epitope-specific CTLs in vivo. Moreover, the plasmid vector functioned as a gene vaccine; NP epitope-specific CTLs were primed in vivo upon transfection of the vector into dermis by electroporation. The results suggest that this epitope-based DNA delivery system may provide a new strategy for in vivo induction of epitope-specific CTLs to investigate antigen processing and presentation.

Amino Acid Sequence↗

Tumor necrosis factor alpha: posttranscriptional stabilization of WAF1 mRNA in p53-deficient human leukemic cells.

The p53 protein directly regulates the expression of the WAF1 (wild-type p53-activated fragment 1) protein which is a cyclin-dependent kinase inhibitor (CDK1). DNA damaging agents such as ionizing or UV radiation, and some chemical agents induce WAF1 in wild-type p53 containing cells, thereby halting cell cycle progression. WAF1 expression is also induced through a p53-independent pathway. Tumor necrosis factor alpha (TNF alpha) is a cytotoxic/cytostatic compound for some human cancer cells. We examined a series of myeloid leukemic cell lines that expressed either no p53 (HL-60, K562) or mutant inactive p53 (KG-1, KCL22,THP-1, U937). The KG-1, HL-60, K562, and KCL22 myeloid leukemic cells increased their levels of WAF1 mRNA in the presence of TNF alpha. We focused on KG-1 cells to determine how TNF alpha modulated WAF1 expression. WAF1 mRNA increased in a dose-dependent manner in the cells after exposure to increasing concentrations of TNF alpha, and this increase occurred in the absence of new protein synthesis. An increase of WAF1 protein and a concominant decrease of cyclin-dependent kinase 2 activity also was found in KG-1 cells. Flow cytometry using 5-bromo-2'-deoxyuridine showed an increase in the proportion of TNF alpha- treated KG-1 cells in the G0/G1 phase of the cell cycle. TNF alpha enhanced the rate of WAF1 transcription only 1.4 fold in TNF alpha-treated KG-1 cells as compared to untreated cells. Notably, however, the half-life (t 1/2) of WAF1 mRNA in TNF alpha-treated cells was 2.5 hours as compared to 0.5 hours in untreated cells. These results indicate that TNF alpha increases WAF1 levels at least in part via a postttranscriptional stabilization of the mRNA; and TNF alpha may mediate its cytostatic effects through WAF1 in some cell types.

CDC2-CDC28 Kinases↗

Effects of cyclopiazonic acid and thapsigargin on electromechanical activities and intracellular Ca2+ in smooth muscle of carotid artery of hypertensive rats.

1. The effects of cyclopiazonic acid (CPA) and thapsigargin (TG), both of which are known to inhibit sarcoplasmic reticular Ca(2+)-ATPase, on the mechanical activities, intracellular Ca2+ level and electrical activities of smooth muscle of the carotid artery of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY) were compared. 2. Both CPA and TG induced elevation of tension of the smooth muscle, which was composed of a phasic and a tonic component. The level of tension attained, especially the tonic component, was greater in the preparation from SHRSP. 3. The elevation of tension was associated with an increased intracellular Ca2+ level. Both the elevation of tension and the increase in intracellular Ca2+ were diminished by the removal of extracellular Ca2+ or by the application of verapamil. 4. The resting membrane potential of the preparations from SHRSP were depolarized to a greater extent than those from WKY.CPA depolarized the smooth muscle from both SHRSP and WKY, and the final level was also more depolarized in the preparation from SHRSP. 5. These results indicate that the elevation of tension induced by these drugs is mainly due to increased Ca2+ influx through voltage-dependent Ca2+ channels, and the difference in the action between the preparation from SHRSP and that from WKY can be explained mainly by the changes in the channels. 6. Thus, differences in the action of these drugs on the tension of smooth muscle between preparations from WKY and SHRSP can mainly be explained by the difference in the membrane potential which is related to the difference in voltage-dependent Ca2+ influx.

Animals↗

Antigenicity of cell wall mannans of Candida albicans NIH B-792 (serotype B) strain cells cultured at high temperature in yeast extract-containing sabouraud liquid medium.

Cultivation of Candida albicans NIH B-792 (serotype B) at high temperature (37 degrees C) for 48 h in yeast extract-containing Sabouraud liquid medium (YSLM) provided the following findings in comparison with the findings obtained after incubation at 27 degrees C. Growth of the blastoconidia of this strain was decreased, with a dry weight of 9%, and the cells were deficient in cytokinesis. The cells did not undergo agglutination with serum factor 5 from a commercially available serum factor kit (Candida Check). Mannan (B-37-M) obtained from the cells cultured at 37 degrees C had partially lost its reactivity against serum factor 4 and lost most of its reactivity against serum factor 5 in an enzyme-linked immunosorbent assay (ELISA) in contrast to that (B-27-M) at 27 degrees C. Both cells and mannan prepared by cultivation first at 37 degrees C and then at 27 degrees C entirely recovered their reactivities with serum factors 4 and 5. 1H-nuclear magnetic resonance analysis also revealed that B-37-M had lost a beta-1,2-linked mannopyranose unit and retained a phosphate group. Similar changes were observed in the three other serotype B strains used in the study. The beta-1,2-linked mannooligosaccharides longer than mannotetraose were not included among the products released from B-37-M by mild acid treatment. The results of the inhibition ELISA with a series of beta-1,2-linked mannooligosaccharides from biose to octaose (M2 to M8, respectively) showed that the reactivity against serum factor 4 was inhibited most strongly by the oligosaccharides M4 to M8 and that the reactivity against serum factor 5 was inhibited completely by relatively longer oligosaccharides, M5 to M8, indicating their participation as the antigenic factor 5 epitopes.

Agglutination Tests↗

Novel functional polymers: poly(dimethylsiloxane)-polyamide multiblock copolymer. V. The interaction between biomolecules and the surface of aramid-silicone resins.

Multiblock copolymers consisting of aromatic polyamide(aramid) and poly(dimethylsiloxane) (PDMS) aramid-silicone resins (PASs) were synthesized by low temperature solution polycondensation, and PAS films were prepared by casting from an N,N'-dimethylacetamide solution. In this study, we investigated bovine serum albumin (BSA) adsorption, L929 cell adhesion, and tissue reaction on the surface of PAS in order to clarify the interaction between PAS and biomolecules. It was found that the amount of adsorbed biomolecules on PAS was extremely low in contrast with those on aramid and nylon films, and it was comparable to SILASTIC 500-1 film. This suppression of adsorption of biomolecules onto PAS seemed to be due to the low surface free energy of the outermost surface of PAS, where PDMS block was condensed.

Adsorption↗

Evaluation of biological responses to polymeric biomaterials by RT-PCR analysis. I. Study of IL-1 beta mRNA expression.

In this study, we introduce a novel research methodology, the evaluation of mRNA expression of cells contacting with polymeric materials using reverse transcription-polymerase chain reaction (RT-PCR) analysis HL-60 was used as a model of the macrophages. The expression of interleukin-1 beta (IL-1 beta) mRNA, a cytokine secreted by macrophages, was selected to estimate the extent of inflammation. The expression of IL-1 beta mRNA in the HL60 cells cultured on various substrates and in various conditions was studied. Expression of IL-1 beta could be successfully determined by RT-PCR analysis. A 48 h incubation period was necessary to clarify the expression of IL-1 beta mRNA. It became clear that lipopolysaccharide stimulation was not necessary in this analysis because of the high sensitivity of RT-PCR analysis. It is concluded that RT-PCR analysis is a powerful tool for studying cell-polymer interaction, and is a complementary method for ELISA.

Base Sequence↗

IL-1 induces expression of WAF1 mRNA in human fibroblasts: mechanisms of accumulation.

WAF1 inhibits cyclin-cyclin dependent kinase complexes, causing arrest in the cell cycle. We report that interleukin-1 (IL-1) regulates the levels of WAF1 protein and mRNA in human fibroblasts. Further studies showed that 12-O-tetradecanoyl phorbol 13-acetate (TPA) enhanced the accumulation of WAF1; cells refractory to TPA still increased their levels of WAF1 mRNA when exposed to IL-1. IL-1 also increased transcription of WAF1 by 13-fold and WAF1 mRNA became 2-fold more stable in cells stimulated with IL-1 (t1/2 = 2 h) as compared to untreated cells (t1/2 = 1 h). In summary, IL-1 induces expression of WAF1, and this occurs by increased transcription of WAF1 and stabilization of WAF1 mRNA. Our data also indicate that the induction of WAF1 mRNA by IL-1 occurs through a pathway independent of protein kinase C activation.

Cell Line↗

Administration of recombinant human IL-1 by Staphylococcus enterotoxin B prevents tolerance induction in vivo.

Peripheral tolerance is important to prevent autoimmunity of T cells against tissue-specific autoantigens in peripheral organs. In certain pathologic situations, peripheral tolerance breaks for unknown reasons and autoimmune diseases occur. Anergy is one of the mechanisms of peripheral tolerance that down-modulates IL-2 synthesis and IL-4 responsiveness by helper T cell clones. In this report, we utilized a model system in which V beta 8+ CD4 T cells were anergized by administration of high doses of Staphylococcus enterotoxin B (SEB) in vivo and investigated an effect of recombinant human (rh) IL-1 on the tolerance induction. RhIL-1 was used because of its ability to induce IL-4 responsiveness in T cells. When rhIL-1 was administered within 24 h after SEB inoculation, the cytokine interfered with tolerance induction; V beta 8+CD4 T cells from mice that had been treated with both SEB and IL-1 proliferated in response to SEB and produced IL-2, IL-4, and IFN-gamma upon TCR/CD28 cross-linking. Delayed administration of rhIL-1 by 48 h failed to do this; T cells did not proliferate in response to SEB, but they retained an ability to produce IL-4 upon TCR/CD28 cross-linking. Administration of rhIL-1 induced better proliferation of V beta 8+CD4 T cells in response to SEB in vivo but did not prevent cell death after proliferation. These results suggest a potential role of inflammatory cytokine IL-1 in the course of autoimmunity via interference with tolerance.

Animals↗

Irradiation induces WAF1 expression through a p53-independent pathway in KG-1 cells.

WAF1 binds to cyclin-Cdk complexes and inhibits their activity, causing cell cycle arrest. Previous studies have shown that expression of WAF1 is induced through the p53-dependent pathway; WAF1 is induced in cells with functional p53 but not in cells with either mutant p53 or no 53. Human myeloblastic leukemia cells KG-1 had no constitutive expression of p53, and irradiation did not induce p53. However, irradiation increased WAF1 expression in KG-1 cells and other cell lines containing mutant p53. The KG-1 cells constitutively produced low levels of tumor necrosis factor (TNF); irradiation markedly increased the production of TNF. Notably, induction of WAF1 mRNA by irradiation was blocked by anti-TNF antibody. Furthermore, exogenously added TNF increased levels of WAF1 mRNA in these cells. Irradiation increased the rate of WAF1 transcription 3-fold, and the half-life (t1/2) of WAF1 mRNA in these cells increased from < 1 h in unirradiated cells to > 4 h in irradiated cells. These findings indicate that increased levels of WAF1 transcripts occur, at least in part, through a pathway of TNF production and that the increase in WAF1 mRNA observed after irradiation is regulated by both transcriptional and posttranscriptional mechanisms. Our present study strongly suggests that an alternative pathway of induction of WAF1 occurs independent of activation by p53.

Cell Line↗

Irradiation increases manganese superoxide dismutase mRNA levels in human fibroblasts. Possible mechanisms for its accumulation.

Irradiation induces the production of superoxide radicals (O2.-), which play an important causative role in radiation damage. Manganese superoxide dismutase (MnSOD) is a mitochondrial enzyme involved in scavenging O2..-. This study examined MnSOD gene regulation by irradiation in WI38 human fibroblasts. Unstimulated fibroblasts constitutively expressed MnSOD activity and mRNA; irradiation markedly increased MnSOD activity and mRNA levels. The increase in MnSOD transcripts by irradiation was both time- and dose-dependent. WI38 fibroblasts constitutively produce low levels of interleukin-1 (IL-1). The induction of MnSOD mRNA by irradiation was partially blocked by anti-IL-1 antibodies, and treatment of cells with IL-1 also increased MnSOD mRNA levels. Inhibition of the cyclo-oxygenase pathway with indomethacin augmented the induction MnSOD mRNA by irradiation and prostaglandin E2 inhibited the accumulation of MnSOD mRNA by irradiation. Transcriptional run-on analysis showed that irradiation increased the rate of MnSOD transcription 2-fold. Stability studies of MnSOD mRNA in these cells showed that the half-life increased from < 1.5 h in unirradiated cells to > 4 h in irradiated cells. These results suggest that induction of the MnSOD gene after irradiation is regulated, at least in part, by IL-1 production and that increased levels of MnSOD transcripts also occur through a pathway of endogenous prostaglandin E2 production. Our data indicate that the increase in MnSOD mRNA observed after irradiation occurs through both transcriptional and post-transcriptional mechanisms.

Cells, Cultured↗

Muscle and intramuscular nerve pathology in congenital hypomyelination neuropathy.

Two patients had delayed development and generalized muscle hypotonia and weakness since early infancy. Their muscle biopsies showed slight variation in fiber size without group atrophy, and no clear evidence of an active demyelinating process in the intramuscular nerves. The most striking finding by light microscopy was the absence of myelinated fibers in the intramuscular nerve bundles. Ultrastructurally, the axons were devoid of myelin sheath or had very thin myelin sheaths, and the axons were surrounded by multilayered basal lamina forming an atypical onion bulb with no suggestions of myelin destruction. A sural nerve biopsy from one of the patients showed similar findings. Unlike the Déjèrine-Sottas type of hereditary motor and sensory neuropathy, there was no evidence of demyelination and remyelination in the muscle pathology, suggesting that the poor myelination in congenital hypomyelination neuropathy is due to a true "hypo"-myelination and not the result of demyelination.

Biopsy↗

Impaired CD28-mediated co-stimulation in anergic T cells.

We have investigated a CD28 co-stimulation in anergic T cells in staphylococcal enterotoxin B-inoculated mice by stimulating the cells with a plate-coated anti-TCR antibody in the presence or absence of an anti-CD28 antibody. CD28 co-stimulation increased the levels of IL-2 and IL-4 mRNAs in naive CD4+V beta 8+ T cells. However, it did not increase the levels of IL-4 mRNA at all and only partially increased those of IL-2 mRNA in anergic T cells. It was demonstrated that CD28 co-stimulation was impaired so that it no longer stabilized cytokine mRNAs in anergic cells. The levels of IL-4 mRNA in response to TCR stimulation were higher in anergic T cells than those in naive T cells in spite of the defective CD28 co-stimulation in the former cells. Anergy induction and generation of a Th2-type immune response in vivo are discussed.

Animals↗

Tumor necrosis factor and interleukin-1 synergize with irradiation in expression of GM-CSF gene in human fibroblasts.

Tumor necrosis factor (TNF) and interleukin-1 (IL-1) improve the survival of lethally irradiated animals through production of hematopoietic growth factors. Exposure of fibroblasts to TNF (1000 U/ml) drastically increased granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA at 1 h and the level returned nearly to baseline by 24 h. Levels of GM-CSF RNA were less than basal level at 24 h after exposure to irradiation alone. In contrast, cells cultured with TNF (1 h) and then irradiated, had prominent expression of GM-CSF mRNA at 24 h. Transcriptional run-on analysis has shown that TNF stimulated the rate of GM-CSF transcription by > 10-fold in irradiated cells. Moreover, TNF stabilized GM-CSF mRNA at 24 h after irradiation; 4 increased from < 20 min in untreated cells to > 2 h in cells cultured initially with TNF and followed by irradiation. We repeated the same experiments with IL-1 and found that IL-1 had the same effects on accumulation, transcription, and stabilization of GM-CSF RNA. Our findings indicate that TNF and IL-1 synergize with irradiation in expression of GM-CSF gene in human fibroblasts; this increased expression occurs by enhancement of transcriptional rate and post-transcriptional stabilization of GM-CSF mRNA.

Cells, Cultured↗

In vitro effects of OK-432 on irradiated mouse bone marrow cells.

PURPOSE: In vitro effects of OK-432 on irradiated mouse bone marrow cells are examined. METHODS AND MATERIALS: Bone marrow cells of BDF1 mouse (1 x 10(6) cells/ml) were incubated with alpha medium, 2% fetal calf serum and OK-432 in a CO2 incubator at 37 degrees C for 24, 48 and 72 h, respectively. After centrifugation, each supernatant was collected and used for conditioned medium in CFU-GM assay: Changes in CFU-GM as a function of incubation time and OK-432 dose was examined; changes of CFU-GM according to various doses of OK-432 were examined in two mouse strains, BDF1 and BALB/c mouse; changes in protective effect of OK-432 in terms of CFU-GM as a function of administration timing of OK-432 in relation to irradiation. As a radiation source, 137Cs at a dose rate of 500 cGy/min was used. RESULTS: The CFU-GM decreased with the incubation time when OK-432 was not administered, while it significantly increased with incubation time when OK-432 was added at 0.5 and 1.0 KE/ml at 48-72 h of incubation. The former showed marked increase at 48-72 h of incubation. CFU-GM of BDF1 mouse was always higher than that of BALB/c mouse for any dose of OK-432. CFU-GM per femur according to the timing of administration of OK-432 from 24 h before to 24 h after irradiation showed 10299 +/- 2300 (24 h before), 10783 +/- 2463 (3 h before), 10045 +/- 1501 (immediately after), 8504 +/- 1188 (3 h after), 4898 +/- 1212 (6 h after), 1214 +/- 736 (12 h after) and 181 +/- 113 (24 h after irradiation), respectively. CONCLUSION: OK-432 stimulates cultured mouse bone marrow cells to produce GM-CSF in vitro by direct contact action. This direct stimulating action of OK-432 on GM-CSF production of bone marrow cells can be kept from 24 h before to at least 3 h after irradiation.

Animals↗

Number and location of AUUUA motifs: role in regulating transiently expressed RNAs.

Many RNAs coding for either cytokines or oncogenes are unstable and have a short half-life (t1/2). The AUUUA motif is a highly conserved sequence and is repeated three or more times in the 3' untranslated region (3'UTR) of RNAs encoding many of these short-lived cytokines and oncogenes. These sequences can confer instability. In this study, we investigated the role of number and location of AUUUA motifs in stabilization of RNA. We introduced 1xATTTA, 2xATTTA, ATTTTTTTA (second adenosine of 2xATTTA was substituted with a thymidine), 3xATTTA, 5xATTTA, 7xATTTA [AT-rich sequence from granulocyte-macrophage colony-stimulating factor [GM-CSF] gene (AT-62)], and GC-62 (GC sequences were substituted for ATTTA sequences in the 7xATTTA) into the 3'UTR of rabbit beta-globin (R beta G) gene. This construct also contained the neomycin-resistance gene. These expression vectors were transfected into human lung fibroblasts (W138), which constitutively expressed low levels of GM-CSF mRNA. Stable transfectants were selected by growth in G418. Northern blot analysis of actinomycin D-treated, stably transfected cells demonstrated that the number of AUUUA sequences correlated with rapidity of turnover of the chimeric R beta G mRNA. The rank order of stability was GC-62 = 1xATTTA = 2xATTTA (no RNA decay at 4 hours) > 3xATTTA = 5xATTTA (t1/2, 4 hours) > 7xATTTA (t1/2, 2 hours). Stability of mRNA of R beta G also was reduced (t1/2, 2 to 4 hours) when AT-62 was introduced into the second exon of R beta G gene. In these same cells, the t1/2 of GM-CSF RNA was approximately 10 to 15 minutes, suggesting that the AUUUA motifs cannot alone account for the rapid degradation of this cytokine mRNA. Phorbol diesters, including 12-0-tetradecanoyl phorbol 13-acetate (TPA), stabilize a variety of transiently expressed RNAs, including GM-CSF RNA. We found that TPA markedly increased (> 30-fold) the accumulation of GM-CSF RNA. In contrast, TPA was unable to stimulate the levels of the chimeric R beta G when either 1x, 2x, 3x, or 5xATTTA motifs were fused to 3'UTR, or when either AT-62 or GC-62 control sequences were fused to the second exon. The chimeric beta-globin construct with either AT-62 or ATTTTTTTA in the 3'UTR had only an approximately twofold to threefold increase in accumulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Irradiation increases expression of GM-CSF in human fibroblasts by transcriptional and post-transcriptional regulation.

Fibroblasts produce a variety of cytokines including granulocyte/macrophage colony-stimulating factor (GM-CSF). GM-CSF is pivotal for proliferation and function of myeloid cells. In this report, we describe the regulation of GM-CSF gene by irradiation in human fibroblasts. We found that fibroblasts constitutively produced GM-CSF; irradiation markedly increased the production of GM-CSF. The increase in GM-CSF transcripts by irradiation was both time- and dose-dependent. Moreover, irradiation increased GM-CSF mRNA in cells with prolonged exposure to 12-O-tetradecanoyl-phorbol-13-acetate (TPA). WI38 fibroblasts constitutively produce low levels of IL-1. Induction of GM-CSF mRNA by irradiation was partially blocked by anti-IL-1 antibodies. On the other hand, inhibition of prostaglandin synthesis did not affect induction of GM-CSF RNA. Transcriptional run-on analysis showed that irradiation increased the rate of GM-CSF transcription. Stability studies of GM-CSF mRNA in these cells showed that half-life (t1/2) increased from < 20 min in unirradiated cells to > 100 min in irradiated cells. These findings suggest that the increase in GM-CSF mRNA observed after irradiation is regulated by transcriptional and post-transcriptional mechanisms. Our results indicate that induction of GM-CSF gene by irradiation requires de novo protein synthesis and increased levels of GM-CSF transcripts also occur through a pathway distinct from protein kinase C activation.

Dose-Response Relationship, Radiation↗

Immobilization of human thrombomodulin onto poly(ether urethane urea) for developing antithrombogenic blood-contacting materials.

Thrombomodulin (TM) is a newly described endothelial cell-associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. In this study, focussing on the application of TM for biomedical materials, recombinant human TM (hTM) was immobilized onto the polymers for medical use, and the evaluation of their antithrombogenicity and the interaction with platelets were investigated. As the base polymer for immobilization reaction, poly(ether urethane urea) (PEUU), which was reported to have good blood compatibility, was used. hTM-immobilized PEUU showed superior antithrombogenic activity, such as the prolongation of plasma recalcification time and the inhibition of thrombin-induced platelet aggregation, though the amount of immobilized hTM was very small (i.e. less than 1 microgram/cm2). Platelet adhesions onto hTM-immobilized PEUU were not observed. These results show that the immobilization of hTM does not change the native good blood compatibility of PEUU, but provides excellent anticoagulant activity.

Antithrombins↗

Immobilization of human thrombomodulin on biomaterials: evaluation of the activity of immobilized human thrombomodulin.

Thrombomodulin (TM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. In this study, the immobilization of hTM was investigated in detail using surface modified polymers. As the basis of immobilization, poly(acrylic acid) (PAAc) surface-grafted poly(ethylene) (PAAc-g-PE) film was used with the expectation of increasing the immobilization amount of hTM. The effect of the immobilization reaction on the hTM activities, and the comparison of the activities of the immobilized hTM with the free hTM, were studied.

Acrylic Resins↗